EARTH × TECHNOLOGY

Four and a Half Billion Years

1956 CE

Phanerozoic · Cenozoic · Quaternary · Holocene · Meghalayan

Clair Patterson measured lead isotopes in meteorites, and in deep-ocean sediment standing in for the planet as a whole, and arrived at 4.55 billion years: Earth and the meteorites, he argued, formed from the same material at the same time. A clean measurement meant first removing the lead that leaded petrol had spread over everything, his own laboratory included, which is how a geochemist came to spend the rest of his career fighting the fuel industry.

Why it matters

This is the number that sets the scale of everything here: the left edge is Patterson's measurement, and sixty years of refinement have moved it by less than one per cent. It is also a reminder that the instrument is part of the world it measures. He could not read the age of the Earth until he had subtracted us from it.

Dating & uncertainty

The figure of 4.55 billion years is an age for meteorites, carried over to the Earth on the argument that both formed from the same material at the same time; what later work has examined is that assumption, and how long the Earth itself took to assemble.

Sources

1. Patterson (1956), Geochimica et Cosmochimica Acta · Age of meteorites and the Earth
2. Halliday & Canup (2022), Nature Reviews Earth & Environment · The accretion of planet Earth

Earth history as one day

23:59:59.99871.3 ms before midnight

if Earth’s 4.54 billion years were compressed into a single day